1. Field
Embodiments of the present invention relate to a hydraulic shock absorber interposed between a vehicle body and a wheel for absorbing shock from a road surface.
2. Description of the Related Art
A conventional hydraulic shock absorber includes a cylinder, a piston rod having a slidable piston inserted in the cylinder, an oil passage formed in the piston so as to make the communication of oil chamber defined on both sides of the piston, and a bypass passage formed in the piston rod so as to make the communication of the oil chambers. Further, in order to reduce a change in attitude of a vehicle body in the case of maximum expansion of the hydraulic shock absorber, the sectional area of the bypass passage is reduced by using an open/close rod to thereby increase a damping force (see Japanese Patent No. 3887107, for example).
In the hydraulic shock absorber described in Japanese Patent No. 3887107, a damping force can be increased in the case of maximum expansion by reducing the sectional area of the bypass passage. However, a push rod is used to reduce the sectional area of the bypass passage, causing a cost increase. Further, no consideration is given to the complete closure of the bypass passage.